1. Field of the Invention
The present invention relates to the improvement of a numerically controlled system and a numerical control method employed to control a machine tool, for example.
2. Description of the Related Art
In the prior art, upon working a die or mould having a free-form surface, tool path data are formed by representing approximately the tool path by infinitesimal segments such as a straight line, a circular arc, a curve, etc. when the tool is moved virtually by using the CAD/CAM system so as to come into contact with the free-form surface, and then the cutting is executed by providing such tool path data to the numerically controlled machine tool.
In general, in case the curved surface working is executed by the numerically controlled machine tool, the number of tool path data items consisting of the infinitesimal segments and formed by the CAD/CAM system is enormous. In particular, in recent working by the high speed cutting, a method is employed so that a surface close to a specular surface can be produced by reducing the working pick feed to be as small as possible and thus the burden of the subsequent polishing step can be reduced or the polishing step can be omitted.
In such working, the working precision must be improved by increasing the number of the tool path data items prepared by the CAD/CAM system. Therefore, the number of the tool path data items prepared by the CAD/CAM system is increased and also the data transferred to the numerically controlled system becomes enormous.
Also, sometimes correction of the tool diameter is needed on the spot because tool wear and tool exchange. However, in three-dimensional curved-surface working, it is difficult to correct an offset distance since such a surface is often cut by a ball end mill. Therefore, since the enormous number of tool path data must be calculated again and again using the CAD/CAM system, the operation efficiency is substantially reduced.
As a system to overcome the above problem, there exists the system set forth in Patent Application Publication (KOKAI) Hei 11-15513, for example. In this system, the mould shape data generating function portion for generating the mould shape data based on the curved surface data indicating the curved surface to be worked (referred simply to as xe2x80x9ccurved surfacexe2x80x9d or xe2x80x9cworked curved surfacexe2x80x9d hereinafter) and the tool path data forming function portion for forming the tool path data from the mould shape data are provided to the calculation processing unit. Then, the tool path data can be output in an on-line fashion from the mould shape data generating function portion to the tool path data forming function portion and other cuffing devices. Also, the formation of the tool path data and the cutting can be executed concurrently.
However, in the numerically controlled system of the prior art, since the tool path data are formed from the mould shape data, a large amount of tool path data must also be formed. Also, since evaluation of the worked curved surface is not performed, the working precision cannot be improved by setting appropriately the working speed, i.e., the moving speed of the tool, in response to the worked curved surface.
In addition, if the formation of the tool position data is not in time, movement of the tool must be stopped in the course of working or refuge of the tool must be made. If the tool is stopped in motion or escaped in the middle of working, sometimes that portion remains as the scratch-like tool trace.
The present invention has been made to overcome above problems, and it is an object of the present invention to provide a numerically controlled system and a numerically controlling method described as follows.
a. The preparation of tool path data transmitted to the numerically controlled system from a CAD/CAM system in the prior art can be omitted, and a tool position as a process applying portion position can be decided based on a shape of a worked surface of a working object as a processed surface of a processing object.
b. It is not needed that the conventional tool path data should be calculated again by using the CAD/CAM system to change the conditions of the process applying portion, more particularly, to correct the tool diameter because of the tool wear or the tool exchange, for example.
c. The speed of the process applying portion can be set appropriately in accordance with the state of the processed surface, while suppressing the increase of the number of the tool position data as the process applying portion position data.
d. The generation of the scratch-like trace, etc. of the process applying portion can be prevented by preventing generation of the stop or the refuge of the process applying portion in the middle of process.
e. The processed quality can be improved without damage of the productivity.
In order to achieve the above object, a numerically controlled system of the present invention comprises evaluating means for forming evaluation data by arranging virtually a process applying portion of a system to be numerically controlled on a given scheduled path locus not to interfere with a processed surface of a processing object and by setting a plurality of evaluation points to evaluate a state of the processed surface; command speed deciding means for deciding a command speed, at which the process applying portion is moved, based on the evaluation data; and process applying portion position data forming means having process applying portion position deciding means for deciding a process applying portion position to be given to the numerically controlled system based on the command speed and a shape of the processed surface such that the process applying portion does not interfere with the processed surface; wherein an operation of the evaluating means and an operation of the process applying portion position data forming means are executed in real time.
Therefore, since the command speed at which the process applying portion is moved is decided based on the evaluation data, the appropriate command speed can be decided in response to the state of the processed surface. Also, since the process applying portion position is decided by arranging virtually the process applying portion to come precisely into contact with the processed surface, increase of an amount of data to be prepared can be suppressed. In addition, since the formation of the evaluation data and the decision of the process applying portion position are executed in real time, the overall processing time can be shortened. Accordingly, the quality of the process can be improved without damage of the productivity.
Then, the process applying portion position data forming means includes process applying portion position data storing means for storing process applying portion position data and process applying portion position data number monitoring means for issuing a deceleration command when a data number stored in the process applying portion position data storing means is less than a predetermined value, and the command speed deciding means decides the command speed based on a moving standard speed and the deceleration command.
Therefore, since the process applying portion speed is decelerated by issuing the deceleration command when the data number of the process applying portion positions is reduced smaller than the predetermined value, it can be prevented that the decision of the process applying portion position is not performed in time in the middle of processing and thus the movement of the process applying portion is stopped. As a result, it is possible to prevent generation of the scratch-like tool traces, etc. due to the stop of the tool.
In addition, the evaluating means includes evaluation data storing means for calculating a curvature of the processed surface of a processing object at evaluation points and a moving standard speed of the process applying portion to correspond to the curvature as evaluation data and storing the evaluation data, and evaluation progress state monitoring means for issuing a speed limiting command when a number of the evaluation data stored in the evaluation data storing means is reduced smaller than a predetermined value, and the command speed deciding means decides the command speed based on a moving reference speed and the speed limiting command.
Therefore, since the process applying portion speed is decelerated by issuing the deceleration command when the number of the evaluation data stored in the evaluation data storing means is reduced smaller than the predetermined value, it can be prevented that the decision of the process applying portion position is not performed in time in the middle of processing and thus the movement of the process applying portion is stopped. As a result, generation of the scratch-like tool traces, etc. due to the stop of the tool can be prevented.
Further, the evaluating data storing means stores the evaluation data in unit of segment that is classified from a predetermined start point to a predetermined end point on a scheduled path locus, and evaluation progress state monitoring means for issuing a speed limiting command when a unit number of the segment stored in the evaluation data storing means is reduced smaller than a predetermined value.
Therefore, since the process applying portion speed is decelerated by issuing the deceleration command when the unit number of the segment in the evaluation data stored in the evaluation data storing means is reduced smaller than the predetermined value, it can be prevented that the decision of the process applying portion position is not performed in time in the middle of segment and thus the movement of the process applying portion is stopped. In addition, since normally no trouble is caused by stopping once the process applying portion at the end point of the segment, it can be prevented that the process applying portion is stopped in the middle of the segment by handling the evaluation data in unit of segment. As a result, it is possible to prevent generation of the scratch-like tool traces, etc. due to the stop of the tool by preventing stop of the tool in the course of the segment.
Besides, a numerically controlling method of the present invention comprises the steps of forming evaluation data by arranging virtually a process applying portion of a system to be numerically controlled on a given scheduled path locus not to interfere with a processed surface of a processing object and by setting a plurality of evaluation points to evaluate a state of the processed surface; deciding a command speed, at which the process applying portion is moved, based on the evaluation data; and deciding a process applying portion position to be given to the numerically controlled system based on the command speed and a shape of the processed surface such that the process applying portion does not interfere with the processed surface; wherein formation of the evaluation data and decision of the process applying portion position are executed in real time.
Therefore, since the command speed at which the process applying portion is moved is decided based on the evaluation data, the appropriate command speed can be decided in response to the state of the processed surface. Also, since the process applying portion position is decided by arranging virtually the process applying portion to come precisely into contact with the processed surface, increase of an amount of data to be prepared can be suppressed. In addition, since the formation of the evaluation data and the decision of the process applying portion position are executed in real time, the overall processing time can be shortened. Accordingly, the quality of the process can be improved without damage of the productivity.